XB270HU Laggy in windows

Hello everyone,

I am a proud keeper of the XB270HU and I have a problem which I am going to try to describe it as understandable as I can.

So i got the new Acer XB270HU and I before I got my new PC I went to a friend and tested the monitor.

Everything was working properly, G-Sync on WQHD and no input lag or anything else.

Especially I was able to "feel" the 120+ HZ refresh rate in the desktop already when I was just dragging a folder from the right to the left or in circles.

I knew, that this is +120HZ because I was still able to read everything without any problems.

My friend was using a Nvidia gtx 980TI.

So then I got my own PC (without a graphics card first) and I took the graphics card of my friend to prepare my PC for everything up.

And then while gaming I could also confirm, that everything is working properly like G-Sync or 144 HZ.

And NOW I am coming to my problem:

When i am in the desktop, and moving a folder around or just the mouse, I can already see it is laggy and not really smooth. I tried setting the refresh rate to 60 Hz and back to 120, 144 HZ but it did not change anything.

Now I got my own graphics card which is the gtx 1080 and the problem is still there and I know that it has nothing to do with the graphics card because my Monitor refresh rate is still 144HZ but in Windows it does not feel smooth at all.

When i am in Chrome or Firefox and using testufo I am getting also 144 HZ refresh rate, and to be honest, in most of the websites, scrolling feels really smooth and is readable.

So my conclusion is, that this has something to do with my windows and / or drivers.

I tried downloading and installing the monitor drivers of Acer and the only thing which changed was that in my device manager the "Monitor" went to "XB270HU". 

So it recocnized the fitting driver but was still not able to fix the problem.

And I really dont know what to do else and what I did probably wrong.

So if you guys could help me I would be very greatfull.

Thank you very much !